Apparatus for method for repair of tires



y 27, 1947- E. E. LAKSO 2,421,101

APPARATUS AND METHOD FOR REPAIR OF TIRES Filed May 18, 1944 HIGH FREQUENCY OS CILLATOR INVENTOR Ez'no ELa/Z'So ATTO R N EYS Patented May 27, 1947 APPARATUS AND METHOD FGR REPAIR OF TIRES Elno E. Lakso, Fitchburg, Mass., assignor to Clarence W. Vogt, Norwalk, Conn.

Application May 18, 1944, Serial No. 536,068

11 Claims.

This invention relates to the repair of pneumatic tires by the action of a high frequency electrostatic field, and relates more particularly to the heating effect in said field, and which causes the vulcanization of the uncured rubber applied in the area to be repaired.

In my prior application Serial No. 507,940, I have illustrated an apparatus for tire repair which includes a pair of electrodes disposed on opposite sides of the wall portion to be repaired, and connected to a suitable source of vhigh frequency current, to produce an electrostatic field. The electrodes are shown as spaced from the tire by deformable pads of suitable dielectric material such as sand.

In the prior application Serial No. 514,542, filed December 16, 1943, by Clarence W. Vogt and myself,there is shown means for automatically breaking an electric circuit when the temperature adjacent to the surface of the tire wall has been raised to that required for the desired vulcanization.

The present invention is an improvement on the apparatus shown in said applications, and involves a new method of effecting the temperature control.

One object of the present invention is to secure a more uniform distribution of the heating effect, and particularly in the area where the repair is to be effected and the applied rubber is to be vulcanized. In the ordinary tire there are incorporated a plurality of layers of fabric, such as cords, adjacent to the inner surface. This fabric is also fairly close to the outer surface in the areas of the side walls and beads, but along the tread portion there is a considerable thickness of rubber outside of said fabric. The dielectric constant of the fabric and the rubber are not the same, and there is a tendency for the fabric to become heated more rapidly, or to a higher temperature, than the outer rubber layer.

In carrying out my present invention, I apply to the outer surface of the tire, and between the tire and-the outer electrode, a material having substantially the same dielectric constant as the fabric of the tire, so that the rubber to be vulcanized is disposed between two layers of material which have about the same dielectric constant, and thus the rubber throughout the area between said layers may b heated substantially uniformly. r

A further object of the invention i to provid an improved means for breaking the circuit producing the heating effect when the desired temperature is reached.

In carrying out my invention there is employed a strand or thread of a material which has high tensile strength at atmospheric temperature, but low tensile strength at the temperature to which the rubber is heated to eil'ect vulcanization. One end of the strand is clamped between the tire and one electrode, and th other end is held under tension, which when released by the breaking of the strand, will cause the breaking of the electric circuit. The strand may be of various different materials having the desired characteristics, but a thread of vinylidine chloride polymer, sold under the trade-name Saran" has been found Very satisfactory.

As a further feature I provide a. tube through which the strand may extend, and which may be detachably secured to the tire to hold the strand in place during the application of the pads and electrodes, and the application of pressure. After the clamping, the tube may be pulled out along the strand to leave the inner end tightly clamped and the outer portion in the groove remaining after pulling out the tube. Thus the tension may be applied to the inner clamped end, and with comparatively little clamping effect on the remaining portion between the electrodes, so that this outer portion may readily pull out when the heating adjacent to the clamped part of the strand is sufllcient to cause the reduction of tensile strength to the point where the strand breaks under the tension applied.

In the accompanying drawings:

Fig, 1 is a top plan view of a portion of the apparatus, including the upper electrode and a5 pad Fig. 2 is a side elevation of the apparatus shown in Fig. 1, with a wall of a tire in place between the electrodes.

Fig. 3 is a section similar to Fig. 2, but showing a portion of the tire adjacent to the tread in position between the electrodes, said section being taken at right angles to the direction of the strand.

Fig. 4 is a side elevation of certain of the parts shown in Fig. 2, and

Fig. 5 is an end view of the strand retaining member detached from the rest of the apparatus, and shown on a larger scale.

In the apparatus as illustrated, a tire wall A is clamped between two electrode carriers l0 and II having electrodes l2 and I3 carried thereby. Between the outer electrode l2 and the outer surface of the tire there is provided a bag I which may be formed of canvas and filled with a granular or pulverulent dielectric material,

such as sand, or analogous material such as mineral or glass wool. Between the inner electrode i3 and the inner surface of the tire wall there is disposed a similar bag lb.

The tire wall A is shown as having a plurality of layers of cord or other fabric 18 adjacent to its inner surface embedded in rubber and a layer of rubber C, the major portion of which is outside of the layers of fabric, but which is integral with the rubber dispersed throughout the fabric, so as to form an integral wall.

In carrying out my invention I place to the outer surface of the tire over the area to be vulcanized, a plurality of layers IQ of fabric, the number of layers and the character of the fabric approximating the layers B of fabric within and adjacent to the inner surface of the tire except that it is not impregnated with or embedded in rubber. Therefore, a high frequency current is delivered to the electrodes i2 and II to form a high frequency electrostatic field between said electrodes, the outer applied fabric l8 will be heated to substantially the same temperature as the inner layers of fabric B of the tire, and to a somewhat higher temperature than the layer C of rubber, but the rubber to be vulcanized being spaced from each electrode by the same general character of pad, and by substantially the same general character of fabric layers, will be heated uniformly, and the temperature at the outer surface of the area to be vulcanized will be substantialiy the same as that at the innermost portion of the recess which was filled with the uncured rubber.

Obviously the size, area and depth of the area to be vulcanized will vary with the character of the repair. I have shown in Fig. 2 an area D of unvulcanized rubber which has been applied in making the repair.

In Fig. 3 I have shown substantially the same construction as in Fig 2. but taken transversely of the tire rather than circumferentially along a wall thereof, and have shown a part of the tread with the repair area D near the shoulder of the tread. This view show more clearly the variation in the thickness of the rubber portion of the tire and the outer layers l8 following the contour of the outer surface of the tire. It also shows more clearly how the outer canvas bag Il may conform to the surface of the tire and permit the use of an electrode ii of standard curvature to apply to a wide variety of sizes and shapes of tires.

The electrodes may be connected by cables l1 and is to the terminals of a suitable apparatus it, including a high frequency oscillator for producing the desired current. This apparatus is may be a portable unit and receive alternating current from any desired source. The supply of current to the electrodes is controlled by a switch 20 which may be mounted on the side of the apparatus is. The switch may be operated by a bell crank lever 2| pivoted on a pin 22 and having stops 23 and 2| for limiting the extent of its movement. A coil spring 25 encircles the pivot pin 22 and normally tends to swing the lever 2| clockwise from the position shown in Fig. 1 to force the short arm 26 of the lever against the button 21 for operating the switch to break the circuit. A spool 30 carrying a strand 3| of a material such as Saran, having high tensile clamped to the outer end of this lever by a clamping screw I2.' Thus the spring 2| tends to swing the lever clockwise, and puts the portion of the strand between the end of the lever and the tire under tension. Obviously the degree of tension may be varied by adjusting the spring. A spring I! may act on the spool to prevent unwinding of the latter when the apparatus is not in use.

If the portion of the strand between the fabric layers [8 and the outer bag it be clamped as tightly at the outer line of contact of the bag and fabric as it is over the area D to be vulcanized, the portion of the strand directly adjacent to said area may be heated to a higher temperature than that at the edge of the clamping area, and the strand will not give a t l i has b en heated to reduce its tensile strength to the breaking point at the outer edge of the clamped area. Furthermore, in assembling the parts and adjusting them preparatory to vulcanizing, the strand may be displaced laterally, or not accurately placed in respect to the area to be vulcanized. Therefore there is provided a positioning member which also serves to insure the clamping of the strand over the area D to be vulcanized more tightly than the portion adjacent to the edge of the clamping area. This positioning member is shown as a metal block I! having a tube ll extending therethrough and having pins 81 extending at an angle to one surface of the block IS. The strand may bethreaded through the tube so that when, the apparatus is not in use, or during actual vulcanizing' the tube and block may be disposed on the strand between the spool ill and the clamp 32, as shown in Figs. 1 and 4.

When a repair is to be made, and after the uncured rubber has been applied to the tire, the block 35 is placed on the surface of the tire and pushed along the surface so that the pins 81 extend into the rubber at a small angle to the surface of the latter, and the tube 3! extends to a point closely adjacent to the edge of the area D of the unvulcanized rubber. The strand is extended beyond the end of the tube and across said area. After the electrodes have been tightly clamped in position. with the tube between I the outer bag H and the fabric layers I, and

strength at atmospheric temperature is mounted the strand clamped to the lever 1| with the strand under tension, the tube is pulled out and placed near the spool. In pulling out the tube a small groove 40 will be left along the inner surface of the bag It, and in which the strand will be only loosely clamped. Beyond the end of this groove, which would be beyond the initial position of the tube 38, the strand will be tightly clamped. Thus when the strand becomes heated to the breaking point in the area directly above the rubber being vulcanized, the portion of the strand between that area and the spring pressed lever Il may pull out, regardless of the temperature of the strand at the outer edge of the pressure area between the electrodes. Thus the strand will break when the proper temperature has been reached at the area D, and regardless of the temperature at any other point along the length of the strand.

The swinging of the lever II under the action of the spring 2!, upon the breaking of thestrand, may be noted by the operator, who may then open the circuit to the electrodes and stop f r a ther vulcanization. Thus in some'cases it is not necessary to open the switch 2| by the action of said lever automatically upon the breaking of the strand.

The strand stretches but little under the tension applied, and may elongat somewhat while the temperature is being raised. The tensile strength drops very rapidly in a comparatively close high temperature range, and the strand may greatly elongate before breaking. This range is approximately the temperature of the rubber at the time the vulcanization has been substantially completed and the rubber has acquired the desired condition as to hardness, toughness and resiliency. The breaking point of the strand may be varied by varying the composition or the cross-section thereof and the ten-.

sion of the spring 25.

The member for holding the strand in place during the assembly of the apparatus parts preparatory to vulcanizing is shown as having a tube andthe upper or outer electrode carrier maybe,

adjustable toward and from the inner one to permit the tire wall to be placed in position, and' to force the outer carrier and electrode downwardly to clamp the part of the tire wall to be repaired, under the desired pressure, as shown in my prior application Serial No. 528,396.

The rubber to be vulcanized in the area to be repaired, as well as the rubber of the tire itself, may be natural rubber, synthetic rubber, or any other compound suitable for tire construction or repair. Therefore by the term "rubber as used herein, I include any form of rubber or suitable rubber substitutes. I also use the terms "uncured and "vulcanize in a broad sense, to. include the soft plastic repair material and the action which takes place by heat and pressure to convert it into a resilient form analogous to that of the rubber of the tire.

The term fabric is used to mean those substantially non-stretchable, non-metallic elements commonly used in tires, and regardless of whether they be woven or used as separate, generally parallel cords.

In the construction illustrated the two electrodes are on opposite sides of the tire wall, and are also oppositely disposed in respect to the area to be vulcanized. For the purposes of this invention, and so 'far as concerns certain aspects of it, the two electrodes may be oppositely disposed in respect to the area to be vulcanized, although both on the same side of the tire wall, for instance as shown in companion application Serial No. 514,542, hereinbefore referred to. As the use of a deformable pad between an electrode and the tire wall is not in itself a novel feature of the present invention, it will be evident that therein adjacent to me inner surface and a thicker layer of rubber substantially free of fabric at the outer surface, said method includingappiying uncured rubber to the tire section to be repaired, applying to the outer surface of the tire at said repair section a layer of material having substantially the same dielectric constant asthe fabric incorporated inthe inner portion of the tire wall, and producing a high frequency electrostatic field including said fabric and said mater a 2. The method of repairing a tire by vulcanizing uncured rubber at the area of the tire wall to be repaired, said wall h'aving'layers of fabric therein adjacent to the inner surface and a thicker layer of rubber substantially free of fabric at the outer surface, said method including applying uncured rubber to the tire section to be repaired, applying to the outer surface of the tire at said repaired section a layer of material having substantially the same dielectric constant as the ,fabric incorporated in the inner portion of the tire wall, clamping the tire wall and said material between a pair of electrodes, and producing a high frequency electrostatic field between said electrodes.

3'. The method of repairing a tire by vulcanizing uncured rubber at the area of the tire wall to be repaired, said wall having layers of fabric therein adjacent to the inner surface and a thicker layer of rubber substantially free of fabric at the, outer surface, said method including applying uncured rubber to the tire section to be repaired, applying to the outer surface of the tire at said repair section a layer of material having,

substantially the same dielectric constant as the fabric incorporated in the inner portion of the tire wall, clamping the tire wall and said material between a pair of electrodes, said electrodes being spaced from said tire wall and said material by deformable pads, and-producing a high frequency electrostatic field between said electrodes.

4. The method of repairing a tire by vulcanizing uncuredrubber at the area of the wall to be repaired, which includes clampingbetween an electrode carrier and the tire wall a strand of a material having high tensile strength at atmospheric temperature and low tensile strength at the temperature at which the uncured rubber becomes vulcanized, applying sufficient tension to said strand to break the latter when it is heated to the temperature required for vulcanizing the uncured rubber, producing an electrostatic field including the area to be vulcanized, and by a high frequency electric current, and breaking the circuit of said current upon the breaking of said strand.

5. The method of repairing a tire by vulcanizing uncured rubber at the area of the wall to be repaired, including clamping across the area to be vulcanized a strand of a material having high tensile strength at atmospheric temperature and low tensile strength at high temperature, producing an electrostatic field including the area to be vulcanized, putting th strand under tension, and terminating the production of said field when said strand breaks upon being heated to the temperature at which the vulcanization of the uncured rubber has been eil'ected.

6. An apparatus for repairing tires by the vulcanization of uncured rubber at the area to be repaired, including a non-metallic strand of a material having high tensile strength at atmospheric temperature and low tensile strength at high temperature, means for clamping a portion or the strand across the area to be vulcanized, means for putting said strand under tension,

means for producing an electrostatic held in the area of the uncured rubber, and means for terminating the production of said field in response to the breaking of said strand.

.7. An apparatus for repairing tires, including a pair of electrodes, a pair of deformable pads, means for clamping the tire wall between said pads and said pads and wall between said electrodes, means for producing an electrostatic held between said electrodes, a non-metallic strand disposed between one electrode and the tire wall, means for putting said strand under tension. and means for terminating the production of said held in response to the breaking of the strand.

8. An apparatus for repairing tires. including a pair of electrodes adapted to be positioned with the tire area tobe repaired therebetween, a nonmetallic strand of a material having high tensile strength at atmospheric temperature and low tensile strength at high temperature, means for putting said strand under tension with a portion of it clamped in juxtaposition to the area to be repaired, means for putting said strand under tension, and means for terminating the production of the electrostatic held in response to the ing a tube through which a strand may extend to tire wall over the area to be vulcanized, and between said electrode carrier and the tire. a protecting device for holding a strand in place over 40 2,341,517

the area to be vulcanized and preventing the 8. application of pressure to an outwardly extending portion of said strand, and thereby forming a groove in the wall of said pad during the appli. cation of pressure to said pad, whereby upon moving said device a portion of the strand is loosely held in said groove of said pad.

11. An apparatus for repairing tires by Vulcan. izing uncured rubber at the area to be repaired, including a deformable pad having a flexible wall, a pair of electrodes, means for compressing said pad and the tire between said electrodes, a nonmetallic strand having high tensile strength at atmospheric temperature and low tensile strength at the temperature required for vulcanizing, and having a portion disposedbetween said pad and said tire wall, means for placing said strand under tension, means -for producing a high frequency electrostatic held between said electrodes. means for appb'ing to said strand sumcient tension to break the strand when it reaches the temperature required for the desired vulcanization, and means for breaking the circuit to said electrodes. said means being held inoperative by said strand during the vulcanization.

EINO E. LAKBO.

REFERENCES crrEn' The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name' Date 719,946 Lomer Feb. 8, 1903 1,246,471 Rump! NOV. 13, 1917 2,280,771 Dufour et al Apr. 28, 1942 2,075,486 Van Dyke Mar. 30, 1937 1,911,894 Heintz May 30, 1933 2,340,692 Ridd Feb, 1, 1944 2,324,068 Crandell July 13, 1943 H1111 Feb. 15, 1944 

